c# winforms DataGridView KeyDown appears twice

Question

Please, what is wrong with this code:

InitializeComponent();
this.KeyDown += new KeyEventHandler(dgvC_KeyDown);
---
private void dgvC_KeyDown(object sender, KeyEventArgs e)
  {
  if (e.KeyValue == 188)
  {
  System.Media.SystemSounds.Beep.Play();
  e.SuppressKeyPress = true;
  }
  if (e.KeyValue == (int)Keys.Delete)
  {
  MessageBox.Show("323");
  }
  }
MessageBox appears twice !!

I want to execute some code if comma is pressed, and anotehr code ifDelKey is pressed on a DataGridView (dgvC).
MessageBox is just for test.